roll center

Questions:

1.If the roll center height increases what happens to body roll?

2.How will the rolling and non-rolling moment be affected when the roll center is,

1.At the ground plane

2.Below the ground plane

3.In a real vehicle, which roll center – force based or kinematic will be more accurate? Justify your answer (Think hard!)

Answers:

1. Body roll of a vehicle depends upon the distance between the center of gravity and the roll center. If the roll center height is increased, the body roll will decrease. This is because, the leverage arm length (distance between the center of gravity and the roll center) will decrease, thus the moment will decrease.
   
   2.1.At the ground - The rolling moment will be high when it is on the ground whereas on the other hand, the non-rolling moment will be zero Since, there won't be any roll center height, hence the counter moment will be zero. Also, we can see that the leverage arm length is high leading to the greater rolling of the car at the corners.
   
   2.2. Below the ground - More forces will pass through the springs than provided. A negative force is experienced which makes the double wishbone to act reversely to the normal condition. Now, since the distance between the center of gravity and roll center is increased, the vehicle will experience more roll and some amount of anti-roll will also be there.
   
   3. The main purpose of calculating a roll center is to determine the roll couple, which is dependent on the forces. In a real vehicle, force-based roll center will be more accurate. The value of kinematic roll center remains the graphical interpretation and is good only for understanding the roll center stability. Now, in 2d, it is easy to determine the roll center but in real life (3D), force-based roll center is more accurate as it is dependent on the real forces acting on the vehicle such as lateral forces and jacking force.